Leonard Carpenter uses a handheld fogger to kill adult mosquitoes early Monday by Mystic Field in Lakeview. Disease control officials fear there could be many more people infected with West Nile this year after virus activity has grown in many parts of Southern California. So far, Riverside and San Bernardino counties have not experienced a similar increase.

Leonard Carpenter, who uses a handheld fogger to kill adult mosquitoes, walks by a public posting about the spraying of pesticide early Monday next to Mystic Field in Lakeview. So far, Riverside and San Bernardino counties have not experienced the same increase in West Nile virus activity as other parts of Southern California.

Disease control officials fear high numbers of Californians could be infected with mosquito-borne West Nile virus for the third straight year after activity has spiked in Los Angeles, Orange and San Diego counties and the Central Valley.

While Riverside and San Bernardino counties have escaped similar increases so far, the Inland region is facing a renewed threat from St. Louis encephalitis after the disease was found in both counties following long absences.

The agencies also are stepping up efforts to kill the mosquitoes that spread West Nile after the numbers of infected dead birds, mosquitoes and sentinel chickens are rising higher than this time last year in parts of Southern California and the Central Valley.

“There is the potential for many more West Nile human cases this year,” said Dr. Vicki Kramer, chief of the California Department of Public Health’s Vector-Borne Disease Section.

Most infected people have no symptoms, which can include fever, headache, body aches, joint pains, vomiting, diarrhea or rash. Those most at risk for serious neurological illness from the virus are the elderly and very young, pregnant women and people with compromised immune systems.

On Aug. 5, State Health Officer Dr. Karen Smith reported California’s first death from the disease this year. An elderly person died recently in Sacramento County, which leads the state with 344 dead birds and 340 mosquito samples found with West Nile. Samples usually range from 10 to 50 mosquitoes, but some programs, like San Bernardino County’s, will turn in even one insect.

The number of people infected with West Nile statewide was 10 as of Aug. 5 — roughly half the 22 people who were found with the disease this time last year.

However, the number of dead wild birds sent in to the state — 834 — has more than doubled since the same time in 2015. And nearly 510 more infected mosquito sampleswere turned in statewide compared to early August last year.

This year’s elevated activity comes after California was hit with a record 53 West Nile deaths in 2015 — a number that dwarfed such deaths in every other state last year and far surpassed those reported in California in any previous year.

The 860 Californians infected with West Nile last year also outpaced the disease’s impact elsewhere in the country.

Riverside and San Bernardino counties are seeing lower numbers of infected birds and mosquitoes so far. That’s a good sign, said San Bernardino County Environmental Health Services Mosquito and Vector Control Program Manager Jason Phillippe, adding the county hasn’t found any infected dead birds this year.

“But of course, we want people to remain vigilant because that could change at any time. We don’t want people to let their guard down,” Phillippe said.

Orange County and especially Los Angeles County have significantly more infected birds and mosquitoes than last year. Los Angeles County also has far more infected sentinel chickens.

Greater Los Angeles County Vector Control District officials are concerned at the activity level. Spokesman Levy Sun said that’s because the risk of people getting sick from West Nile is at a near-five-year high.

“This year is trending to be another peak for the virus,” he said. “It sort of has been simmering in the background really quietly. Now it’s starting to boil over.”

A new concern has surfaced in Riverside and San Bernardino counties after St. Louis encephalitis has cropped back up.

Two infected chickens in Needles, reported Aug. 8, are the first sign of the virus in San Bernardino County since 1997. After the virus showed up last year in the Coachella Valley for the first time in a decade, via five mosquito samples, 26 samples have been found in 2016.

Migrating birds may be bringing the disease here, or it may have been here undetected, said Coachella Valley Mosquito and Vector Control District interim Laboratory Manager Jennifer Henke.

Mosquito specialists will watch how West Nile virus interacts with St. Louis encephalitis. They don’t want residents to get sick from either one, Henke said.

“It takes just one bite for somebody to get sick,” she said.

FACTBOXES

LAST YEAR’S NUMBERS

California

Human cases: 860 (783 with symptoms)

Deaths: 53

Riverside County

Human cases: 141

Deaths: 6

San Bernardino County

Human cases: 60

Deaths: 3

Los Angeles County

Human cases: 300

Deaths: 24

Orange County

Human cases: 97

Deaths: 8

Source: California Department of Public Health

WEST NILE SYMPTOMS

Most infected people don’t have symptoms from West Nile virus or St. Louis encephalitis. Those most at risk for serious neurological illness from the sometimes fatal diseases are the elderly and very young, pregnant women and people with compromised immune systems.

Suzanne Hurt has written about everything from boxcar tramps and crooked politicians to surf kayaking, flash floods and the vanishing Borneo rainforest. She’s worked as a reporter at the legendary wire service City News Bureau of Chicago and daily newspapers, The Register-Guard and The Modesto Bee, after a stint as an editor. As a freelancer, she produced hard news and nature, science, adventure travel and extreme sports content, including multimedia. For The Press-Enterprise and Southern California News Group, Suzanne specializes in narrative storytelling, backed by extensive hard news experience, strict journalism standards and a master’s in literary nonfiction from the University of Oregon’s journalism school. She’s told the story of one person’s survival of the Sept. 11 attack on the World Trade Center, traced a man’s path out of homelessness and recreated the Dec. 2, 2015, terrorist attack in San Bernardino through first responders’ eyes. Also covering GA and the environment, she’s written about avalanche danger, canyoneering, snowshoeing, desert and waterfall hikes, cowboy movers, rescue divers, rabid bats, stealthy burros, the mother orange tree scientists won’t let die and the Jesus pancake.

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